This invention relates to the modification of geotextile tubes and more particularly to the repair of holes in geotextile tubes, to the preparation of inlets and other openings into geotextile tubes and to mechanical seaming of geotextile fabric for replacement or attachment of geotextile tube components.
Geotextile tubes are a relatively recent development in coastal engineering and are large sand filled fabric tubes used to control erosion, protect structures, promote dune building, protect or create environmentally sensitive habitat and the like. Even more recently, geotextile tubes have been proposed for dewatering municipal and industrial waste slurries and providing a technique for handling municipal and industrial particulate byproducts or wastes. Geotextile tubes are a tough coarsely woven fabric, known as a geotextile, perhaps thirty feet in periphery and of considerable length. As used in coastal engineering applications, they are placed in the desired position and then filled with sand by pumping water into the tube and then pumping a sand-water slurry into the geotextile tube and displacing the water. The geotextile is designed to be sufficiently permeable to allow the water to escape, leaving the tube filled with sand. Sand is a term of the trade because the material pumped into the geotextile tube is more accurately described as clastics or particulate earth materials, the proportion of sand to clay, or sand to shells or sand to organic material being whatever is available in the area. An example of a geotextile tube is found in U.S. Pat. No. 5,158,395. As used in handling municipal and industrial slurries, the geotextile tubes are filled by pumping the slurry into the tubes which dewater the slurry and contains the particulates.
Geotextile tubes are manufactured by sewing together the edges of large tough woven fabric mats and are offered commercially by several manufacturers, such as TC Mirafi of Pendergrass, Ga. Geotextile tubes are generally made to order so the length and periphery is determined from engineering considerations and the geotextile tubes made accordingly. Geotextile tubes are sewn at a manufacturing facility to the desired periphery and cut to the desired length. When filled, geotextile tubes are not cylindrical but have a generally flat bottom mimicking the underlying ground surface and arcuate sides and tops so the resultant structure is somewhat ovoid.
One of the problems with geotextile tubes is faced during construction because suitable inlets have to be provided for pumping sand into the geotextile tube and the inlets have to be closed on completion. Another problem with geotextile tubes involves the development of openings or tears in the fabric allowing the sand to wash out, particularly if the geotextile tube is subject to wave action. Inadvertent tears or openings develop over the years from a variety of causes such as imperfect factory sewn seams, UV damage to the fabric, punctures, tears or mechanical abrasion as may occur when driftwood is beaten by waves against the geotextile tube.
The current approach is to close the inlet openings and any inadvertent tears or openings by sewing the edges of the fabric together in the field. These hand sewn repairs have not withstood the test of time.
Disclosures of general interest relative to this invention are found in U.S. Pat. Nos. 649,415; 2,620,852; 4,036,674; 5,023,987 and 6,013,343.
This invention is directed to the closing of inadvertent openings in an existing geotextile tube, the preparation of inlet openings and their closing when the geotextile tube is filled and the provision of seams mechanically joined in the field. Several considerations dominate this analysis. First, the load on the geotextile tube is quite large, as can be imagined by the weight of a sand filled tube having a 30xe2x80x2 periphery. This has proved to be the ultimate factor defeating field sewing a patch onto the tube. In a way, this has been a surprise because the strength of the material around any inadvertent opening has adjusted to accommodate any force attempting to increase the size of the opening and has stopped any tear. In reality, what has occurred is that the material around the opening has temporarily stopped the tear. When the material inside the tube shifts or wave action recommences, the opening enlarges. This corroborates the belief that the largest forces applied to the tube occur when filling the tube or when sand inside the tube is shifting in response to movement of fill out of an opening. Second, the interior of the geotextile tube is inaccessible by which is meant that the interior of the tube is not accessible except through the opening that is to be closed. Thus, one cannot insert a large rigid structure through the opening into the tube unless the opening is significantly longer than it is wide.
On reflection, it is apparent that the preparation of an opening for use as an inlet and its ultimate closing is the same problem as the closing of an inadvertent opening. In this invention, a backing member larger than the opening is passed through the opening into the geotextile tube. The backing member is connected by fasteners extending through the geotextile to a support on the outside of the geotextile tube to provide a clamp for clamping a closure member over the opening. In one embodiment of this invention, the backing member may be a split ring so the edge of the fabric opening is placed through the slit and the ring rotated so it is advanced into the interior of the geotextile tube. In another embodiment of this invention, the backing member is split into segments which are separately passed through the opening into the interior of the geotextile tube and then assembled.
An important feature of this invention is the provision of friction enhancers acting between the backing member and the inside of the geotextile tube and/or between the support and the outside of the geotextile tube. When sliding across each other, the backing member, support and geotextile tube fabric exhibit relatively low coefficients of friction. When clamped together with spaced apart fasteners, the fabric between the fasteners tends to move, under load, relative to the fasteners thereby placing the entire load on the fabric immediately adjacent the fasteners. In this invention, friction enhancers are provided between the backing member and the fabric and/or between the support and the fabric so the load applied to the fabric is not concentrated immediately around the fasteners. In other words, the friction enhancers change the connection from a bearing connection effective over a small area around the fasteners to a friction connection effective over a much larger area. The larger area of the connection of this invention reduces the force applied per unit area to the assembly thereby providing a more durable connection.
The same technique that is used to repair an inadvertent opening is used to prepare an inlet opening so that fill material may be pumped into the geotextile tube. The support on the outside of the geotextile tube provides a through passage and a bearing surface to receive a fabric conduit providing a flow passage for a sand-water slurry. One or more bands are applied between the bearing surface and the fabric conduit. When the tube is filled, the bands and fabric conduit are removed and the opening through the support is closed.
In another aspect of this invention, a connection is made between the geotextile and another fabric, such as a UV protection cover by advancing a connection through the fabric in a manner similar to advancing the split ring through the opening into the geotextile tube. In this embodiment, a helical spring is advanced through the weave of the geotextile and the second fabric to make a connection and the helical spring is locked against normal spreading.
It is an object of this invention to provide an improved geotextile tube.
Another object of this invention is to provide a geotextile tube having an opening modified by an improved technique.
A further object of this invention is to provide an improved method of modifying a geotextile tube.
A still further object of this invention is to provide an improved mechanical seam for geotextile tubes.
These and other objects of this invention will become more fully apparent as this description proceeds, reference being made to the accompanying drawings and appended claims.